1    package graphics.graph; 
2     
3    import java.awt.*; 
4     
5    public class ImagePanel extends Panel 
6            /** 
7             *  The responsibility of this class is to provide an instance of a 
8             *  Panel that knows how to interface with the GraphManager. All it 
9             *  really does accept update the update message and cutils.delegate it 
10            *  appropriately. 
11            */ { 
12       private static ImagePanel ip = new ImagePanel(); 
13       private GraphManager gm; 
14    
15       private ImagePanel() { 
16       } 
17    
18       public static ImagePanel getImagePanel() 
19               /** 
20                *  Static getter to support the singleton design pattern. 
21                * 
22                *  @return ImagePanel 
23                */ { 
24           return ip; 
25       } 
26    
27       public void setGraphManager(GraphManager graphManager) 
28               /** 
29                *  Set the GraphManager. Even though GraphManager is a singleton, 
30                *  we didn't want to set it at instantiation time because ImagePanel 
31                *  (this) is also a singleton and GraphManager has a reference to this. 
32                *  To avoid confusion of circular instantiating, GraphManager sends 
33                *  a message here when it is ready to become referenced. 
34                * 
35                *  @param GraphManager 
36                */ { 
37           gm = graphManager; 
38       } 
39    
40       public synchronized void update(Graphics g) 
41               /** 
42                *  Delegate the particulars of updating to the GraphManager. 
43                * 
44                *  @param Graphics 
45                */ { 
46           gm.update(g); 
47       } 
48   }